Gas Metal Arc Welding (GMAW) and Metal Core Arc Welding (MCAW) are arc welding processes commonly used in industry. Several modes of metal transfer are provided by these processes, including pulsed spray transfer, sometimes referred to as pulse welding. Pulsed spray transfer offers many advantages over other transfer modes including low heat input, low spatter operation, as well as the ability to operate over a wide procedure range. In classic pulse welding theory, the welder output is characterized by a series of high amplitude pulses imposed over a lower amplitude background output, with each pulse ideally transferring a single droplet of molten metal across the welding arc from a consumable wire to the workpiece. With advances in high speed industrial controllers and power inverters, pulse welding parameters may be adjusted to optimize the metal transfer for a given welding application. Most modern pulse welding machines offer several synergic pulse welding modes, with each mode providing a recipe of operating pulse parameters based on wire feed speed for a specific wire type, wire size, gas type, etc. The pulse welding electrical waveform is generally characterized by four parameters, including pulse amplitude, pulse duration, background amplitude, and cycle period or frequency, which together determine the power delivered to the arc. For a given welding consumable, the pulse welding power level is related to a metal melt off rate, and if the process is controlled such that the melt off rate equals the wire feed speed (WFS), the resulting arc length will be at an optimum length. Pulse welding processes may thus provide low heat processes in which the consumable electrode ideally does not contact the weld puddle, where the process is typically performed by high-speed control of the welding signal output in conjunction with wire feed speed control in order to provide a spatterless process that can be performed at a lower heat input than spray or globular transfer methods.
For a given pulse welding process, the pulse waveform is ideally tailored for a specific wire type and size, wire feed speed, deposition rate, and other process specifications, in order to optimize the finished weld quality and reduce the welding time. Modern pulse welding machines feature an adaptive feedback circuit that senses the arc length and modifies, or adapts one or more pulse parameters to maintain the balance of power required to the power supplied and thereby maintain the desired arc length, where the adaptive control operation of the power source is generally preprogrammed and is similar to other feedback systems or algorithms. In practice, the actual arc length is typically measured and compared to a desired arc length with the result being an error term. Based on this error term and a multiplication factor, the feedback system adapts the pulse parameters to maintain the desired arc length. This adaptive control works as long as the adaptive routine does not attempt to modify the pulse parameters beyond physical limitations. For instance, if the pulse amplitude is too low, the current may drop below the pulse transition current and droplets will no longer transfer to the puddle. In another situation, if the background amplitude is too low, the arc will pop out and be lost. Other examples include situations in which the pulse period is too long, where conventional adaptive pulse welding controls will cause the molten droplets to become too large to transfer properly, as well as conditions in which the pulse period becomes too short, where prior adaptive techniques cause the peak profiles to run into each other, causing loss of the effect of the pulsing action. Due to these limitations, the range of conventional adaptive pulse welding controls is limited, whereby there is a need for improved adaptive welding systems and methods.